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Molecular dynamics investigations of mechanical behaviours in monocrystalline silicon due to nanoindentation at cryogenic temperatures and room temperature.

Du X, Zhao H, Zhang L, Yang Y, Xu H, Fu H, Li L - Sci Rep (2015)

Bottom Line: Molecular dynamics simulations of nanoindentation tests on monocrystalline silicon (010) surface were conducted to investigate the mechanical properties and deformation mechanism from cryogenic temperature being 10 K to room temperature being 300 K.By searching for the presence of the unique non-bonded fifth neighbour atom, the metastable phases (Si-III and Si-XII) with fourfold coordination could be distinguished from Si-I phase during the loading stage of nanoindentation process.The Si-II, Si-XIII, and amorphous phase were also found in the region beneath the indenter.

View Article: PubMed Central - PubMed

Affiliation: School of Mechanical Science and Engineering, Jilin University, Renmin Street 5988, Changchun, Jilin 130025, China.

ABSTRACT
Molecular dynamics simulations of nanoindentation tests on monocrystalline silicon (010) surface were conducted to investigate the mechanical properties and deformation mechanism from cryogenic temperature being 10 K to room temperature being 300 K. Furthermore, the load-displacement curves were obtained and the phase transformation was investigated at different temperatures. The results show that the phase transformation occurs both at cryogenic temperatures and at room temperature. By searching for the presence of the unique non-bonded fifth neighbour atom, the metastable phases (Si-III and Si-XII) with fourfold coordination could be distinguished from Si-I phase during the loading stage of nanoindentation process. The Si-II, Si-XIII, and amorphous phase were also found in the region beneath the indenter. Moreover, through the degree of alignment of the metastable phases along specific crystal orientation at different temperatures, it was found that the temperature had effect on the anisotropy of the monocrystalline silicon, and the simulation results indicate that the anisotropy of monocrystalline silicon is strengthened at low temperatures.

No MeSH data available.


Related in: MedlinePlus

Lateral cross-sectional view of the transformed region at the maximum indentation depth and after unloading at different temperatures: (a) 10 K, (b) 100 K, (c) 200 K, (d) 300 K. The cross-sectional view on the (100) plane is passing through the centre of the simulation model (plane T in Fig. 7).
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f5: Lateral cross-sectional view of the transformed region at the maximum indentation depth and after unloading at different temperatures: (a) 10 K, (b) 100 K, (c) 200 K, (d) 300 K. The cross-sectional view on the (100) plane is passing through the centre of the simulation model (plane T in Fig. 7).

Mentions: Figure 5 shows a lateral cross sectional view of the deformed silicon specimen at different stages of the nanoindentation at different temperatures. The silicon atoms of the specimen are coloured according to their coordination number. The Si-I phase with fourfold coordination is not shown in the diagram. In Fig. 5, it can be seen that the six-coordinated Si-II phase is located in the region beneath the indenter at the maximum penetration depth. Some other six-coordinated atoms are embedded in the five-coordinated atom sea. The two metastable phases, Si-III and Si-XII, are observed around the region containing atoms with fivefold and sixfold coordination. It can be easily seen that the two metastable phases are distributed more regularly at lower temperatures. After unloading, most of the Si-III and Si-XII atoms are transformed to Si-I, while the Si-II phase transforms into the amorphous phase, indicating that the phase transformation from Si-I to Si-III and Si-XII during loading is reversed during unloading, whereas the phase transformation from Si-I to Si-II is irreversible. The amorphous phase is formed in the residual transformed region, containing fourfold, fivefold and sixfold coordination atoms. Since the metastable phases transform back into their original structure, we propose that this transformation is related to the elastic recovery of silicon during the retraction process.


Molecular dynamics investigations of mechanical behaviours in monocrystalline silicon due to nanoindentation at cryogenic temperatures and room temperature.

Du X, Zhao H, Zhang L, Yang Y, Xu H, Fu H, Li L - Sci Rep (2015)

Lateral cross-sectional view of the transformed region at the maximum indentation depth and after unloading at different temperatures: (a) 10 K, (b) 100 K, (c) 200 K, (d) 300 K. The cross-sectional view on the (100) plane is passing through the centre of the simulation model (plane T in Fig. 7).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4633730&req=5

f5: Lateral cross-sectional view of the transformed region at the maximum indentation depth and after unloading at different temperatures: (a) 10 K, (b) 100 K, (c) 200 K, (d) 300 K. The cross-sectional view on the (100) plane is passing through the centre of the simulation model (plane T in Fig. 7).
Mentions: Figure 5 shows a lateral cross sectional view of the deformed silicon specimen at different stages of the nanoindentation at different temperatures. The silicon atoms of the specimen are coloured according to their coordination number. The Si-I phase with fourfold coordination is not shown in the diagram. In Fig. 5, it can be seen that the six-coordinated Si-II phase is located in the region beneath the indenter at the maximum penetration depth. Some other six-coordinated atoms are embedded in the five-coordinated atom sea. The two metastable phases, Si-III and Si-XII, are observed around the region containing atoms with fivefold and sixfold coordination. It can be easily seen that the two metastable phases are distributed more regularly at lower temperatures. After unloading, most of the Si-III and Si-XII atoms are transformed to Si-I, while the Si-II phase transforms into the amorphous phase, indicating that the phase transformation from Si-I to Si-III and Si-XII during loading is reversed during unloading, whereas the phase transformation from Si-I to Si-II is irreversible. The amorphous phase is formed in the residual transformed region, containing fourfold, fivefold and sixfold coordination atoms. Since the metastable phases transform back into their original structure, we propose that this transformation is related to the elastic recovery of silicon during the retraction process.

Bottom Line: Molecular dynamics simulations of nanoindentation tests on monocrystalline silicon (010) surface were conducted to investigate the mechanical properties and deformation mechanism from cryogenic temperature being 10 K to room temperature being 300 K.By searching for the presence of the unique non-bonded fifth neighbour atom, the metastable phases (Si-III and Si-XII) with fourfold coordination could be distinguished from Si-I phase during the loading stage of nanoindentation process.The Si-II, Si-XIII, and amorphous phase were also found in the region beneath the indenter.

View Article: PubMed Central - PubMed

Affiliation: School of Mechanical Science and Engineering, Jilin University, Renmin Street 5988, Changchun, Jilin 130025, China.

ABSTRACT
Molecular dynamics simulations of nanoindentation tests on monocrystalline silicon (010) surface were conducted to investigate the mechanical properties and deformation mechanism from cryogenic temperature being 10 K to room temperature being 300 K. Furthermore, the load-displacement curves were obtained and the phase transformation was investigated at different temperatures. The results show that the phase transformation occurs both at cryogenic temperatures and at room temperature. By searching for the presence of the unique non-bonded fifth neighbour atom, the metastable phases (Si-III and Si-XII) with fourfold coordination could be distinguished from Si-I phase during the loading stage of nanoindentation process. The Si-II, Si-XIII, and amorphous phase were also found in the region beneath the indenter. Moreover, through the degree of alignment of the metastable phases along specific crystal orientation at different temperatures, it was found that the temperature had effect on the anisotropy of the monocrystalline silicon, and the simulation results indicate that the anisotropy of monocrystalline silicon is strengthened at low temperatures.

No MeSH data available.


Related in: MedlinePlus